Speaker
Description
The visible matter in the universe predominantly consists of plasma. Plasma flows are inherently dynamic and often characterized by non-uniform velocity patterns. This differential motion results in a velocity gradient, which gives rise to shear. Shear flows are omnipresent in many astrophysical scenarios such as planetary atmospheres, the solar heliosphere, the accretion and protogalactic disks, etc.
The study focuses on the dynamics of Langmuir modes, waves and shear Langmuir vortices, in kinematically complex astrophysical shear flows. Due to non-self-adjoint behaviour of the equation linked with shear flow dynamics, an alternative nonmodal approach is adopted. For the two-dimensional background flow model, an explicit second-order ordinary differential equation governing the Langmuir dynamics in flows with kinematic complexity is derived. The subsequent analysis of this equation reveals the shear-induced phenomena characterized by asymptotic persistence. This includes exponential growth and vortical solutions interacting with waves, with a distinct ”echoing” pattern. Besides these solutions, the existence of parametrically unstable wave solutions is also expected. The analysis also extends to the more general three-dimensional flow model. The preliminary results obtained for this case are presented in the thesis.
The results obtained within the study is particularly significant in space weather and solar physics, where shear flows and shear-induced phenomena drive various dynamical processes such as the generation of MHD waves, mode coupling and solar wind acceleration.
